Drag coefficient

About: Drag coefficient is a research topic. Over the lifetime, 14471 publications have been published within this topic receiving 303196 citations. The topic is also known as: drag factor.

Sphere wakes in still surroundings at intermediate Reynolds numbers

Abstract: The wakes of spheres in a still environment were studied for sphere Reynolds numbers Re in the range 30-4000. The experiments consisted of towed spheres in quiescent baths of glycerin and water mixtures. Measurements included dye traces illuminated by a laser light sheet for visualization and laser velocimetry for streamwise velocities. The recirculation region on the downstream side of the sphere was stable and symmetric for Re 280. Three wake regions were identified: a fast-decay region that was observed only when vortex shedding was present, followed in succession by turbulent and laminar wake regions. Vortex shedding increased the distance to the onset of the turbulent wake region by an order of magnitude due to the presence of the fast-decay wake region. Mean velocities within the turbulent and laminar wake regions scaled according to classical similarity theories, with transition between these regions at conditions where their estimates of mean streamwise velocities along the axis were the same: this occurred at a local wake Reynolds number ReH -10. Within the turbulent wake region, turbulence intensities along the axis were roughly 85% for Rew > 70; however, as the onset of the laminar wake region was approached, turbulence intensities along the axis were proportional to Rew1/4, which is consistent with scaling proposed earlier for the final decay period of axisymmetric wakes.

Numerical simulation of unconfined flow past a triangular cylinder

Abstract: Numerical simulations of two-dimensional laminar flow past a triangular cylinder placed in free-stream at low Reynolds number (10⩽Re⩽250) are performed. A finite volume method, second-order accurate in space and time, employing non-staggered arrangement of the variables with momentum interpolation for the pressure–velocity coupling is developed. Global mode analysis predicts Recr=39.9 which confirms the results of earlier studies. Vortex shedding phenomena is found to be similar to the square cylinder with no second bifurcation in the range of Re studied. A discussion on the time-averaged drag coefficient, rms of lift coefficient and Strouhal number is presented. Particle tracking and the instantaneous streaklines provide an excellent means of visualizing the von Karman vortex street. Copyright © 2006 John Wiley & Sons, Ltd.

A theoretical study of body drag in subcritical axisymmetric flow.

Abstract: A method of predicting body drag in subcritical axisymmetric flow is outlined which requires only detailed body shape, free-stream conditions and transition point to be prescribed. Results of calculations for a range of body shapes are shown essentially to confirm information in Royal Aeronautical Society Data Sheets but clearly demonstrate that fineness ratio alone is not sufficient to characterise body shape. For example, at a fixed fineness ratio of 0.18, detailed changes in body contour are shown to produce 10 per cent changes in drag coefficient.